Motion-transmitting remote-control assemblies for transmitting motion in a curved path are used in aircraft, automotive, and marine environments. A typical use for such assemblies is to position throttle members in automobiles. In general these assemblies include a flexible tubular conduit movably supporting a flexible motion-transmitting core element with two ends.
Most commonly, the motion-transmitting remote-control assembly is formed as a one piece design, with one end of the assembly connected to a controlling member, e.g., and accelerator pedal, and the other end connected to a controlled member, e.g., a throttle body. In applications such as vehicle engine compartments it is often difficult for assembly line personnel to reach through and around various vehicle components to connect the conduit and core element ends of the one piece assembly to their respective support structures and control linkages after those structures and linkages have already been installed in a vehicle. One way to overcome this difficulty is to form the assembly in two separate pieces having two conduit segments and two core element segments. In this situation each conduit segment is connected to its support structure and each core element segment to its control linkage before installing those structures and linkages in the vehicle. Following installation, the core element segments are later joined together into a single core element and the conduit segments joined into a single conduit.
One reason that the two-piece design overcomes the installation problems associated with the prior art one-piece design is that the two-piece design has only one point of connection after vehicle assembly. It is difficult for an assembler of the one-piece design to take both ends of a single piece assembly and connect each end to its respective support structures and control linkages deep within a crowded engine compartment. It is easier and less time consuming for an assembler to reach and connect the loose ends of an installed two-piece core-cable assembly. It is easier and quicker because the loose ends of an installed two-piece core-cable assembly extend outward from the core-cable assembly mounting points, protrude from between crowded engine compartment structures, and are therefore easier to reach and connect. Easier and quicker assembly reduces assembly line worker fatigue and increases production rate and product quality.
However, state-of-the-art pre-installed two-piece assemblies have an inherent design problem of core element slack. For an assembler to grasp and connect the core element sections of an installed two-piece assembly, the core inner ends must protrude unsheathed from the conduit inner ends. If the core inner ends do not protrude, the assembler cannot grasp and connect them. On the other hand if the core inner ends do protrude, connecting the conduit sections together over the connected unsheathed core sections compresses the connected core sections causing core element slack. Core element slack causes the core element to bend or kink within the connected conduit or at the unsheathed portion of the core between a conduit outer end and a control linkage.
Core element slack is a problem because it prevents a motion-transmitting remote-control assembly from functioning properly. For example, in a "pull-only" assembly such as a spring-return throttle actuator, excessive slack results in poor control response. Poor control response results because control inputs to the core element must first take up the core element slack before transmitting any pulling motion to the controlled member. Moreover, in a "push-pull" control system, core element slack will additionally result in core element kinking and bending under compressive loads--effectively precluding any push force transmission to the controlled member.
Some current two-piece assemblies allow their core element inner ends to protrude for splicing, but are unable to hold their conduit segments in a spaced-apart disposition to preclude core element slack. One example of this type of prior art assembly is shown in U.S. Pat. No. 4,218,935 issued May 16, 1972 to Ion et al. This reference discloses two core segments 22, 24, each movably supported within a respective conduit segment 46, 48. The core segments 22, 24 extend unsheathed from their respective conduit segments 46, 48 to allow access to core splicing means 16. The Ion patent also discloses a conduit coupling means in the form of a coupling nut 50 that clamps the conduit segments 46, 48 together end-to-end in a final operative position. The coupling nut 50 is moveable from an initial assembly position that leaves the protruding core segments 22, 24 exposed for splicing. However, the Ion et al. coupling nut 50 cannot lock its conduit segments 46, 48 into a spaced-apart disposition. The coupling nut 50, in its operative position, pulls the conduit segments 46, 48 together into an abutting end-to-end disposition over the spliced core segments 22, 24. In moving to the operative position, therefore, the coupling nut 50 effectively shortens the overall conduit length without any compensating reduction in core element length. As a result, the combined distance that the core segments 22, 24 protrude unsheathed from the conduit segments 46, 48 with the coupling nut 50 in the initial assembly position, is the amount of core slack that results with the coupling nut 50 in the final operative position.